Survival of human T and B lymphocytes after X-irradiation

The survival of unstimulated human T and B lymphocytes after X-irradiation in vitro was measured by Trypan Blue dye exclusion over a period of four days. B cell numbers were observed to decline rapidly even after relatively low doses, but T cell numbers fell much more slowly. A comparison of the percentage survival 96 hours after irradiation shows that in this system T cells are between approximately 2 and 5 times more resistant than B cells. Data for interphase death after 48 hours are compared with cytogenetic data for interphase loss of PHA-stimulated human lymphocytes and are shown to be in broad agreement at radiation doses below 400 rad. It is suggested that at higher doses mitotic delay may be increasingly important leading to selection of non-irradiated cells at 48 hours.